Stationary induction apparatus



Feb. 20, 1923. 1,445,978.

- H. 0. STEPHENS.

STATIONARY INDUCTION APPARATUS.

FILED APR; 30. 192l- Hi S Attorney.

Patented Feb. 20, 1923.

(UNITED STATES I HOWARD O. STEPHENS, OF PITTSFIELD,' MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

STATIONARY INDUCTION APPARATUS.

Application filed April 30, 1921. Serial No; 465,896.

To all whom it may concern Be it known that I, HOWARD O. STEPHENS,

a citizen of the United States, residing at Pittsfield, in the county ofBerkshire, State of Massachusetts, have invented certain new and usefulImprovements in Stationary Induction Apparatus, of which the followingis a specification.

My invention relates to stationary induction apparatus and has for itsobject an improved, economical, and readily manufactured arrangement ofparts.

More particularly my invention relates to transformers adapted forsupplying large currents through circuits connected in multiple.. Suchconnections are frequently required in the industrial consumption ofpower; as for instance, in the multiple electrode type of electricfurnaces.

In multiple connected transformers, a short'circuit-on one secondarycircuit generally-has undesirable reactions (through line regulation) onthe current flowing in the secondary circuit in parallel with it; infurnace work for instance, a short circuit across two electrodes atdifferent potential would reduce the voltage across a pair; in parallelwith it to a point where the arc may go out or else cause theirelectrode adjusting mechanism to operate in a manner which would resultin such'electrodes taking an undue portion of the load.

If the secondary circuits in multiple are on the same magnetic core; theundesirable reactions become more exaggerated than when supplied fromseparate transformers, as the large leaking flux poduced by the shortcircuit curent tends to buckout the inducting or magnetizing flux fromthe other circuit.

By my invention, however, a construction isemployed whereby themultiple. circuits are supplied substantially without undesirable mutualreactions. In my arrangement all the windings belonging to the twocircuits are mounted on the same magnetic core thereby obtaining all theeconomies incident t0 the construction of a single electrical machine.My arrangement involves the separate excitation of each multiplesecondary circuit, and the loose coupling of the same with theirrespective primaries. This may be accomplished by placing eachsecondary' and its associated primary on a separate leg, or each on aseparate portion of the same leg.

For a more complete understanding of the nature and object of myinvention reference should be had to the following detailed descr1pt1ontaken in connection with the accompanying drawing in which:

Fig. 1 is a diagrammatic view of my invention adapted for supplyingcurrent through two circuits in multiple to a multiple electrodeelectric furnace taken as showing atypical load to which my invention isapplicable. Fig. 2 shows one arrangement of windings on a magnetic corein accordance with my invention; while Fig. 3 shows a modification.

Referring now to the drawing, 10 denotes an electric furnace of the arctype having four electrodesll 12, 13 and 14, which is a typicaltranslating device requiring current to be fed thereto in parallelcircuits. In this furnace the electrodes 11 and 12 are supplied withcurrent from the winding 15 which is a secondary of a transformerexcited from the primary 16. Similarly, the electrodes 13 and 14 aresupplied with currentfrom the secondary winding 17 which is excited bythe primary 18. The primaries 16- and 18'are connected in multiple, asshown, to the feeding conductors 19.

In accordance with my invention these windings are mounted on a singlemagnetic core and are arranged so that undesirable mutual reactions areavoided. One such arrangement is shown in Fig. 2 where 20 denotes 'acore assembled preferably from laminated magnetic material. Thesecondary windings 15 and 17 are shown as mounted each on' a separateleg of the core, the primary winding associated with secondary 15 beingcomposed of sections 161, 162, 163 and 16& disposed in spaced relationto each other and to the secondary, the spacing preferably being forrelatively great distances apart so as to secure a. comparativelyloosemagnetic coupling effect.

The same arrangement obtains with reto achieve a similar loose magneticcoupling effect. Consequently the reactance between secondaries 15 and17 and their primaries' 16 and 18 is relatively high.

In Fig. 3 another arrangement of windings in accordance with myinvention is illustrated, whereby the windings are all disposed on asingle core leg. The core 30 is of the sheli type having a singlewinding leg 31 on which the secondaries 15 and 17 are mounted at pointswidely separated. The primary coils 161, 1-62, 163 audios are associatedwith the secondary 15 on the upper half of the leg 31 while primarycoils 181, 182, 183 and 18% are arranged on the lower half andassociated with secondary 17. A loose coupling magnetically between thesecondaries and their associated primaries is arranged for here again,as it is essential that the relative reactance between secondaries andprimaries be relatively high. insulating barrier 35 is also indicated asseparating the upper group of primary and secondary windings from thelower group.

in operation, it is seen that should a short circuit occur across theelectrodes 11 and 12 the consequent rush of current is checked by theself-limiting eiTect of the high inductance of winding15 obtaining byreason of the loose coupling magnetically of winding 15 with its primary16. The current flowing in the primary 16, as a result is not greatlyincreased by the short circuit, thereby avoiding any material impedancedrop in the voltage across the conductors 19 with a consequent drop involtage across the electrodes- 13 and 14. All tendency for the electrodeadjusting mechanism to impose automatically an undue portion of the loadon electrodes 13 and 14, or for the arc thereacross to go out isaccordingly efiectually removed.

Having now described embodiments of my invention which are at presentthe best means known to me for carrying the same into effect, I wouldhave it understood that they are merely illustrative, and that I do What l claim as new and desire to secure 4 by Letters Patent of theUnited States, is 2- 1. ln static-nary induction apparatus, thecombination with a magnetic core, of a plurality of secondaries mountedthereon and adapted to supply current in parallel circuits to a commontranslating device, and primaries separately associated with eachsecondary, loosely coupled magnetically with each other and wit theirrespective secondaries, the separate primaries being connected togetherin multiple,

2. in stationary induction apparatus, the combination with a magneticcore, of a plurality of secondaries mounted on separate parts of saidcore and adapted to supply current in parallel circuits to a commontranslating device, and primaries on each of the separate partsassociated with the secondaries thereon and loosely coupled magneticallywith said secondaries, said primaries being connected together inmultiple.

3. ln stationary induction apparatus, the combination with a magneticcore, of a plurality or" secondaries mounted on separate parts or" saidcore and adapted to supply current in parallel circuits to a commontranslating device, and primary coils associated and grouped with eachseparate sccondary and spaced relatively great tances apart from eachother and from said secondaries, the groups of primary coil being"connected in multiple.

in witness whereof, I have hereunto set my hand this 25th day o1 April,1921.

HUWARD 0. STEPHENS.

